Propionibacterium acnes-related chronic inflammation after cataract extraction and intraocular lens implantation is emerging as a significant clinical problem in this country. This anaerobic organism has now been implicated in numerous clinical reports as part of the etiology of a unique form of persistent and recurrent postoperative inflammation, which can result in visual morbidity. It is not clear whether this inflammation is driven by replicating organisms, resulting in a chronic form of true bacterial endophthalmitis, or whether the organism is acting as an immunomodulator (adjuvant) in the development of a variant of phacoantigenic or phacoanaphylactic endophthalmitis. It is possible that both mechanisms may be operative. The current studies designed to determine the pathogenesis of this newly described postoperative inflammatory syndrome. Specifically, long term natural history studies of P. acnes-induced inflammation and endophthalmitis will be completed in pseudophakic and aphakic laboratory model eyes using viable and non-viable organisms. The adjuvant properties of non-viable P. acnes in the development of phacoanaphylactic endophthalmitis in a laboratory model will be studied. The results of these studies will help elucidate the pathogenesis of this emerging and complex cause of postoperative chronic inflammation.